System for controlling a pneumatic valve of a turbine engine

ABSTRACT

A system ( 110 ) for controlling a pneumatic valve ( 112 ) of a turbine engine, such as a bleed valve, the system comprising a directional control valve ( 140 ) for controlling air under pressure connected between the valve ( 112 ) that is to be controlled, a controlling solenoid valve ( 118 ), and means ( 144 ) for taking off air at a pressure P 1 , the solenoid valve also including a first inlet ( 132 ) connected to a source of fluid at a pressure P 2  that is independent of P 1 , the opening and closing of the pneumatic valve being controlled by a flow of the air at pressure P 1  delivered by the directional control valve that is controlled by the fluid at pressure P 2  delivered by the solenoid valve.

BACKGROUND OF THE INVENTION

The invention relates to a system for controlling a pneumatic valve of aturbine engine, and in particular a pneumatic bleed valve of a turbineengine.

Document EP-B1-0 374 004 describes a bleed valve for a turbine engine.

In general, a turbine engine has at least one bleed valve for bleedingair from the primary stream delivered by the high-pressure compressor ofthe turbine engine during certain stages of operation of the engine,such as starting, accelerating, deceleration, and idling. Air is bledinto the secondary (bypass) stream and serves to impart a greater marginto the high-pressure compressor.

It is known to provide a turbine engine with a pneumatically controlledbleed valve, in which the opening of the valve is controlled by airunder pressure taken form the high-pressure compressor of the turbineengine.

A bleed valve is designed to be in a closed position in normal operationmode. The bleed valve generally needs to be fed with air at a pressuregreater than the bleed pressure from said valve in order to open thevalve, i.e. the air for controlling the valve needs to be taken from astage of the compressor that is situated downstream from the bleedvalve. The valve is closed by interrupting the flow of air forcontrolling the valve.

In the prior art, the bleed valves of a turbine engine are connected tocontrol means that include solenoid valves (i.e. electro-valves orelectrically-controlled valves), each of those solenoid valves having aninlet connected to means for taking off air from the compressor and anoutlet connected to the valve that is to be controlled so as to controlthe valve directly with the air taken from the compressor.

Such a solenoid valve includes an electrical portion that is sensitiveto temperature. It is therefore necessary to avoid mounting solenoidvalves close to the bleed valves where temperatures in operation arerelatively high. Proposals have therefore been made to mount suchsolenoid valves in the nacelle of the turbine engine where ambienttemperatures are much lower.

Furthermore, solenoid valves must not be fed with air that is too hot.The conventional components of such solenoid valves are designed tooperate with feed temperatures of the order of 200° C. to 300° C., whichis well below the temperature of the air used for controlling the bleedvalves, which may be as high as 627° C. or even more (717° C.) in theevent of a fuel metering valve failure leading to over speed.

There is therefore incompatibility between the requirement to have highpressure for controlling opening of the bleed valves and the requirementto have low temperature in the air that is fed to the solenoid valvesfor controlling the bleed valve.

Solutions have already been proposed to that problem.

A first solution consists in cooling the air fed to the solenoid valves,e.g. by convection. Under such circumstances, the air taken from thehigh-pressure compressor flows along pipework in which it is cooled byexchanging heat with the outside environment.

However, that solution cannot be implemented in certain engines, inparticular in those where the air that is taken off is too hot and wouldrequire cooling that is greater than the cooling capacity available fromheat exchange with the environment. Cooling capacity may be low forvarious reasons such as passing through an arm for passing services inan intermediate casing that is poorly ventilated, or the need to lag thepipework in the nacelle in order to avoid skin temperatures exceeding200° C.

Another solution to the above-mentioned problem consists in feeding thebleed valves with air at a pressure that is substantially equal to thebleed pressure of those valves instead of with air at a higher pressure,thus making it possible to reduce the associated temperature. Asdescribed in U.S. Pat. No. 6,981,842, the bleed valve then needs to havea particular configuration (FIGS. 4-6 of U.S. Pat. No. 6,981,842).

That solution is not applicable to engines fitted with high-pressurebleed valves and with solenoid valves having a maximum feed airtemperature of 200° C. Even if the control air for those solenoid valvesis taken at a pressure equivalent to the bleed pressure, the temperatureof the air remains too high since it may be as much as 461° C., or evenmore (543° C.) in the above-mentioned circumstances of a fuel meteringvalve failure leading to over speed.

Finally, a last known solution to the above-mentioned problem consistsin feeding bleed valves with air at a pressure lower than the bleedpressure and thus at temperatures that are lower.

That solution is not satisfactory either since, in order to control ableed valve with air under pressure, if the air is at a pressure lowerthan the bleed pressure of the valve, then the section of the valve mustbe greatly overdimensioned, such that the valve is generally impossibleto incorporate in a turbine engine.

SUMMARY OF THE INVENTION

The object of the invention is to provide another solution to theabove-mentioned problem, making it possible to satisfy both of the aboverequirements (high pressure for opening the bleed valves, and lowtemperature for the air fed to the solenoid valves that control thebleed valves).

To this end, the invention provides a system for controlling a pneumaticvalve in a turbine engine, such as a bleed valve, the system comprisinga controlling solenoid valve and means for feeding fluid at a pressureP2, the system being characterized in that it also includes adirectional control valve for fluid at a pressure P1 that is connectedto the bleed valve, to the solenoid valve, and to means for taking offair at the pressure P1 from the turbine engine in order to control theabove-mentioned bleed valve, opening and closing of the bleed valvebeing controlled by the air at the pressure P1 delivered by thedirectional control valve that is itself controlled by a flow of fluidat the pressure P2 delivered by the solenoid valve, the pressure P1being independent of the pressure P2.

In the system of the invention, the directional control valve (such as adistributor) mounted between the solenoid valve and the pneumatic valvethat is to be controlled connects said pneumatic valve either to themeans for taking off air at the pressure P1 in order to cause it to beopened, or else to the exhaust in order to cause it to be closed, whileit is itself controlled by a fluid that is supplied by the solenoidvalve at a pressure that is independent of the control pressure for thepneumatic valve and that can therefore be lower than said controlpressure, so the fluid may consequently have a temperature that isacceptable for the solenoid valve, e.g. not exceeding 200° C., when thefluid is air taken from a stage of the compressor.

In the present application, the term “independent” is used of pressuresto designate pressures of fluid coming from sources that are differentand/or that have different values. These fluids may for example be takenfrom different stages of the same compressor of the turbine engine; thefluids then have pressures that are different, the pressure of the fluidtaken from the stage that is further downstream being greater than thepressure of the fluid taken from the stage that is further upstream.

The system for controlling the pneumatic valve may thus be considered asa two-stage system, comprising a high-pressure stage including thedirectional control valve and a low-pressure stage including thesolenoid valve (which stage is also a low temperature stage).

The directional control valve may be controlled pneumatically orhydraulically, i.e. the solenoid valve may control it with a flow of airor with a flow of liquid. By way of example, the solenoid valve obtainsits control fluid by being connected to a fuel circuit or to means fortaking off air from the turbine engine.

Advantageously, the directional control valve is of the type havingthree fluid inlet/outlet ports connected respectively to the valve thatis to be controlled, to the solenoid valve, and to the ambientatmosphere, and it includes a movable member that is movable between twopositions in which the valve that is to be controlled is connectedrespectively either to means for taking off air at the pressure P1 or tothe ambient atmosphere, with the movement of the movable member beingcontrolled by the fluid under pressure delivered by the solenoid valve.

The take-off means connected to the directional control valve may takeair from the compressor of the turbine engine from a zone that issituated substantially in register with the bleed valve or elsedownstream from the bleed valve, relative to the flow direction of gasthrough the turbine engine. When this air is taken off downstream fromthe valve that is to be controlled, the taken-off air is at a pressurehigher than the bleed pressure of the bleed valve, and when the air istaken off level with the bleed valve, the taken-off air is at a pressurethat is substantially identical to the bleed pressure of the bleedvalve. Under such circumstances, the bleed valve may include anadditional chamber so as to be able to have a section against which thecontrol pressure acts in order to open the valve that is greater thanthe section against which the pressure acts in order to close the valve.A valve of this type is described in document U.S. Pat. No. 6,981,842.

The solenoid valve may have two inlets for connecting respectively to asource of fluid under pressure and to the ambient atmosphere, and oneoutlet connected to a port of the directional control valve.

Advantageously, one inlet of the solenoid valve is for connecting tomeans for taking off air at a pressure P2 from the turbine engine, thepressure P2 being less than the pressure P1. The solenoid valve is thusconnected to means for taking off air from the compressor of the turbineengine in a zone that is situated upstream from the zone from which airis taken off at the pressure P1 for feeding to the directional controlvalve, “downstream” being relative to the flow direction of air throughthe turbine engine. The solenoid valve is thus fed with air at apressure and at a temperature that are lower than the temperature andpressure of the air that is taken off to feed the directional controlvalve that controls the bleed valve, and the directional control valveis itself controlled by a fluid at low pressure coming from the solenoidvalve in order to switch between the high pressure required foroperating the pneumatic valve, and ambient pressure.

By way of example, the solenoid valve has two chambers, one of which isfor feeding a port of the directional control valve with fluid underpressure, and the other of which is for connecting said port to theambient atmosphere. In a variant, the solenoid valve may be of thetwo-stage type having a first stage for feeding a port of thedirectional control valve with fluid under pressure or with the ambientatmosphere, and a second stage for controlling the switching of thefirst stage.

The present invention also provides a turbine engine, such as anairplane turboprop or turbojet, having an engine surrounded by a nacelleand including at least one pneumatic valve, such as a bleed valve, theturbine engine being characterized in that the or each pneumatic valveis controlled by a system as described above.

The turbine engine may have two or even more bleed valves, each bleedvalve being controlled by a system of the above-described type.

The directional control valve of the system of the invention may besituated in the engine, close to the pneumatic valve that is to becontrolled, or in the nacelle, close to the solenoid valve forcontrolling the directional control valve. Placing the directionalcontrol valve closer to the solenoid valve (in the nacelle) makes itpossible to minimize the volume of the pipe connecting those two piecesof equipment together. Under such circumstances, it is possible to use asimple solenoid valve that has no impact on the configuration of thepneumatic valve. When the directional control valve is placed close tothe pneumatic valve, it is preferably incorporated in the casing of thatvalve so as to reduce the weight of the system. It is then possible touse a simple solenoid valve or on the contrary a two-stage solenoidvalve if the flow rate required for filling the pipework leading to thedirectional control valve is too great.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood and other details, advantages,and characteristics of the invention appear on reading the followingdescription made by way of non-limiting example and with reference tothe accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a prior art system for controllingturbine engine bleed valves;

FIG. 2 is a diagram showing a system for controlling a turbine enginebleed valve in accordance with the invention;

FIGS. 3 and 4 are diagrams showing the directional control valve and thesolenoid valve of the FIG. 2 system, showing respectively the closed andopen positions of those valves; and

FIG. 5 is a diagram of a variant embodiment of the control system of theinvention.

MORE DETAILED DESCRIPTION

Reference is made initially to FIG. 1 which shows a prior art system 10for controlling bleed valves in a bypass turbine engine.

In the example shown, the turbine engine has two bleed valves 12 and 14(specifically “handling” bleed valves HBV1 and HBV2) that are controlledby a common system 10 that also controls an air take-off valve 16 forcontrolling clearance in the engine by using a high-pressure turbineactive clearance control (HPTACC) system.

In known manner, the bleed valves 12 and 14 are mounted in thehigh-pressure compressor of the turbine engine and they enable air fromthe primary stream (at a pressure P0) flowing through that compressor tobe bled off towards the secondary stream F2.

The bleed and take-off valves 12, 14 and 16 in this example arepneumatically controlled, and they are designed to occupy a closedposition in normal operation mode. The bleed valves 12 and 14 need to befed with air at a pressure P1 higher than the bleed pressure P0 forcausing them to open. They are closed by connecting the pressurized airfeed of the valves to ambient pressure.

Typically, each bleed valve 12, 14 may include a chamber that, when fedwith air at a pressure P1, causes a movable member such as a piston tomove from a valve-closed position to a valve-open position, in which airat the pressure P0 of the compressor is bled off into the secondarystream.

The valves 12, 14, and 16 are controlled by respective solenoid valves18, 20, and 22, all of which are mounted in a common pneumatic controlunit (PCU) 24.

The valves 12, 14, and 16 are located in the engine proper 26 of theturbine engine 18, and the solenoid valves 18, 20, and 22 are situatedin the nacelle 28 of the turbine engine, where ambient temperature islower than in the engine proper.

Each solenoid valve 18, 20 has a first inlet 32 connected to means 30for taking air at the pressure P1 from the compressor of the turbineengine, a second inlet 34 connected to the ambient atmosphere Pamb, andan outlet 36 connected to an inlet 38 of the corresponding valve 12 or14, and in particular to the inlet of the above-mentioned chamber ofthat valve.

The PCU 24 includes electrical control means for the solenoid valves 18and 20, which means are suitable for applying a first signal to asolenoid valve in order to cause it to open, i.e. connect its firstinlet 32 fed with air at pressure P1 to its outlet 36 connected to thecorresponding bleed valve 12 or 14, and a second signal for causing thesolenoid valve to close, i.e. to connect its second inlet 34 that isconnected to the ambient atmosphere Pamb with its outlet 36 connected tothe corresponding bleed valve.

As mentioned above, the valves 12 and 14 open when the solenoid valves18 and 20 are open and fed with air at a pressure P1 (higher than thebleed pressure P0). Bleed air then passes through the valves from theprimary stream through the compressor into the secondary stream F2through the turbine engine. The valves 12 and 14 close when the solenoidvalves are closed and connected to the ambient atmosphere Pamb via thesolenoid valves.

This prior art control system 10 presents a major drawback associatedwith the fact that the solenoid valves 18 and 20 are fed with air athigh pressure that is taken from the compressor and that is therefore ata high temperature. That technology is therefore not applicable tosolenoid valves capable of withstanding only relatively lowtemperatures, e.g. not exceeding 200° C.

The present invention makes it possible to remedy that drawback byproviding a bleed valve control system that is of the two-stage type,comprising a high-pressure first stage for controlling the bleed valvesand a second stage at low pressure and at low temperature forcontrolling the first stage. The first stage comprises a directionalcontrol valve for air under pressure and the second stage comprises asolenoid valve that may be fed with fluid at a low pressure and at atemperature that is relatively low, e.g. no more than 200° C.

In the embodiment of the invention shown in FIGS. 2 to 4, the controlsystem 110 has only one bleed valve HBV 112 that is mounted in theengine proper 126 of the turbine engine. This valve 112 is similar tothe valves 12 and 14 of FIG. 1.

In the example shown, the two stages of the control system 110 aresituated in the nacelle 128 of the turbine engine.

The directional control valve 140 forming the first stage of the controlsystem is of the “3/2” type, i.e. it has three ports and two positions.The directional control valve 140 has an inlet 142 connected to means144 for taking air at the pressure P1 from the high-pressure compressorof the turbine engine, an outlet 146 leading to the ambient atmospherePamb, a control inlet 148 connected to the outlet 136 of the solenoidvalve 118, and an outlet 150 connected to the inlet 138 of the bleedvalve 112, i.e. to the inlet of the valve chamber of the above-specifiedtype.

The inlet 148 of the directional control valve 140 is connected to theoutlet 136 of the solenoid valve 118 by a pipe 92 that is relativelyshort so that the solenoid valve and the directional control valve areas close together as possible (while still complying with temperatureconstraints) in order to minimize the internal volume of the pipe 92.

The directional control valve 140 may occupy two states, an open statein which the inlet 142 that is connected to the means for taking off airat the pressure P1 is connected via the outlet 150 to the bleed valve112, and a closed state in which the inlet 146 leading to the ambientatmosphere is connected via the outlet 150 to the bleed valve 112.

The directional control valve 140 is shown diagrammatically on a largerscale in FIGS. 3 and 4. It comprises a member 160, such as a piston,that is mounted in leaktight manner in a cylindrical bore of a valvebody. By way of example, the member 160 comprises two parallel disks 162that are fastened to opposite ends of a longitudinal rod that keeps themspaced apart from each other.

The member 160 defines three chambers in the body of the valve 140. Afirst chamber 164 is defined between one of the disks 162 and an endwall of the body, this chamber communicating with the inlet 148 that isconnected to the outlet 136 of the solenoid valve 118. A second chamber166 is defined between the disks 162, this chamber communicating withthe inlet 142 that is connected to the means for taking off air at thepressure P1 and capable of communicating with the outlet 150 of thedirectional control valve when it is in the above-mentioned open state.A third chamber 168 is defined between the other disk 162 and the otherend wall of the body, this chamber communicating with the inlet 146 thatis connected to the source of air at ambient pressure and being capableof communicating with the outlet 150 of the directional control valvewhen it is in the above-mentioned closed state.

Resilient return means 170, such as a compression spring, are mounted inthe third chamber 168 and urge the member 160 into the closed position(shown in FIG. 3) of the directional control valve. The return force ofthis spring is less than the force exerted by air at pressure P2 on themember 160 when the directional control valve is fed by the solenoidvalve 118.

The solenoid valve 118 that forms the second stage of the control system110 has two inlets and one outlet. Its two inlets comprise respectivelyan inlet 132 connected to means 130 for taking off air at pressure P2from the high-pressure compressor of the turbine engine, and an inlet134 connected to a source of air at ambient pressure Pamb. The outlet136 of the solenoid valve 118 is connected to the inlet 148 of the valve140.

The pressure P2 is less than the pressure P1, and air at the pressure P2is at a temperature that is acceptable for the solenoid valve, e.g. nomore than 200° C. The means 130 for taking off air at the pressure P2are situated upstream from the means for taking off air at the pressureP1 in the compressor and relative to the flow direction of air throughthe compressor.

The solenoid valve 118 is shown diagrammatically at a larger scale inFIGS. 3 and 4. It is of the simple or one-stage type and has twochambers 174 and 172 into which the above-mentioned inlets 130 and 134lead respectively. The chambers 172 and 174 communicate with each othervia a connection port 176, and the outlet 136 of the solenoid valvecommunicates with the chamber 174.

The solenoid valve 118 has a member 180 that is movable between an openposition (shown in FIG. 4) in which the inlet 130 connected to the meansfor taking off air at the pressure P2 is connected to the outlet 136,and a closed position (shown in FIG. 3) in which the inlet 134 connectedto the ambient atmosphere is connected to the outlet 136.

In this example, the member 180 is elongate in shape and has one endcarrying a valve member for closing either the connection port 176between the chambers 172 and 174, or else the inlet port 130 of thechamber 174. The opposite end of the member 180 carries a permanentmagnet that is engaged in a cylindrical coil 182 that is connected to acomputer of the electronic engine controller (EEC) type and toelectrical power supply means.

When the coil 182 is powered, it generates a magnetic field causing themember 180 to move into its position shown in FIG. 3 for closing thesolenoid valve 118, in which the valve member carried by the movablemember closes the inlet port 130 of the chamber 174. The inlet 134 ofthe first chamber 172 then communicates with the outlet 136 of thesecond chamber via the connection port 176. The first chamber 164 of thevalve 140 is then connected by the solenoid valve 118 to the ambientatmosphere. The return means 170 that exert a force on the movablemember 160 greater the force exerted by air at ambient pressure urge themovable member into the closed position of FIG. 3, such that the bleedvalve 112 is connected by the third chamber 168 of the directionalcontrol valve to the ambient atmosphere.

When the coil 182 of the solenoid valve 118 is not electrically powered,the movable member 180 is in its position shown in FIG. 4 for openingthe solenoid valve 118, in which position the valve member carried bythe movable member closes the port for connecting together the chambers172 and 174. The inlet 130 of the chamber 174 then communicates with theoutlet 136 of said chamber. The first chamber 164 of the valve 140 isthen connected via the solenoid valve 118 to the means for taking offair at the pressure P2, thereby causing the movable member 160 of thedirectional control valve to move in the open position shown in FIG. 4,in which the bleed valve 112 is connected by the second chamber 166 ofthe valve 140 to the means for taking off air at the pressure P1.

In normal operation mode, the coil 182 of the solenoid valve 118 ispowered electrically so that it is in its closed position as shown inFIG. 3. The valve 140 is in its closed position and it connects thebleed valve 112 to the source of air at ambient pressure. The bleedvalve 112 thus remains closed.

When the valve 112 is to be opened in order to bleed air at the pressureP0 into the secondary stream, the electrical power supply to the coil182 of the solenoid valve 118 is interrupted by the above-mentioned EECtype means, and the solenoid valve occupies its open position as shownin FIG. 4. The chamber 164 of the directional control valve is fed withair at the pressure P2, thereby causing the movable member 160 to movefrom its position shown in FIG. 3 to its position shown in FIG. 4. Thedirectional control valve thus adopts an open position and connects thebleed valve 112 to the means for taking off air at the pressure P1,thereby causing the bleed valve to open. When electrical power to thecoil 182 is reestablished, the solenoid valve 118 closes (FIG. 3), thechamber 164 of the directional control valve is connected to the ambientatmosphere, and the member 160 is urged by the means 170 to return toits position shown in FIG. 3. The bleed valve 112 is thus connected viathe chamber 168 of the directional control valve to the ambientatmosphere, thereby closing the valve 112.

In a variant, the chambers 172 and 174 of the solenoid valve 118 may beconnected to sources of fluid other than air. For example, they may beconnected to a fuel circuit of the turbine engine. The valve 140 is thenhydraulically controlled, the first chamber 164 being designed to be fedwith fuel.

FIG. 5 shows a variant embodiment of the control system 110′ of theinvention in which the valve 140 is mounted in the engine proper 126 ofthe turbine engine, and is no longer beside the solenoid valve 118 inthe nacelle 182 of the turbine engine. The valve 140 may be mountedinside the casing 190 of the bleed valve 112.

The valve 140 is similar to FIGS. 2 and 4 and its inlet 148 is connectedto the outlet 136 of the solenoid valve 118 via a pipe 192 that islonger than the pipe 92 of FIGS. 2 to 4.

The solenoid valve 118 may be similar to that of FIGS. 2 to 4. In avariant, and as shown in FIG. 5, it may be of the two-stage type. Whenthe pipe 192 connecting the valve 140 to the solenoid valve 118 is long,its internal volume may be large, which may require the solenoid valveto deliver fluid at a high filling rate. Because of significant headlosses in a simple solenoid valve of the type shown in FIGS. 2 to 4, avalve of that type may not be sufficient to deliver the desired flowrate. It is therefore preferable under such circumstances to use atwo-stage solenoid valve, i.e. a solenoid valve having one stage forfeeding the chamber 164 of the valve 140 with the pressure P2 or forconnecting it to ambient pressure, and another stage for controlling theswitching of the first stage.

The operation of the control system shown in FIG. 5 is similar to thatof the control system shown in FIGS. 2 to 4.

In the above-described systems, the pressure P1 for controlling thebleed valve 112 is higher than the bleed pressure P0 of that valve, i.e.the means for taking off air at the pressure P1 are situated in thecompressor downstream from the bleed valve.

In a variant, the control pressure P1 for the bleed valve may be equalto the bleed pressure P0 of that valve, i.e. the means for taking offair at the pressure P1 are situated in the compressor level with or inregister with the bleed valve, i.e. substantially in the same transverseplane as that valve.

Under such circumstances, the pipe used for conveying air under pressurefrom the directional control valve to the bleed valve may be shorter.Furthermore, the bleed valve 112 then includes an additional chamber ofthe type described in document U.S. Pat. No. 6,981,842.

In yet another variant (not shown), the turbine engine may be fittedwith two or more bleed valves that may be controlled independently ofone another by distinct control systems, or that may be controlledsimultaneously by a common control system having one or more directionalcontrol valves and one or more solenoid valves.

The system of the invention may be used for controlling valves otherthan bleed valves.

1. A system for controlling a pneumatic valve in a turbine engine,comprising a controlling solenoid valve and means for feeding fluid at apressure P2, wherein the system further includes a directional controlvalve for fluid at a pressure P1 that is connected to the bleed valve,to the solenoid valve, and to means for taking off air at the pressureP1 from the turbine engine in order to control said bleed valve, openingand closing of the bleed valve being controlled by the air at thepressure P1 delivered by the directional control valve that is itselfcontrolled by a flow of fluid at the pressure P2 delivered by thesolenoid valve, the pressure P1 being independent of the pressure P2. 2.A system according to claim 1, wherein the directional control valve ispneumatically or hydraulically controlled by the solenoid valve.
 3. Asystem according to claim 1, wherein the solenoid valve is connected toa fuel circuit or to means for taking off air from the turbine enginefor the purpose of delivering its control action.
 4. A system accordingto claim 1, wherein the solenoid valve is of the type having three fluidinlet/outlet ports connected respectively to the bleed valve that is tobe controlled, to the solenoid valve, and to the ambient atmosphere, andincludes a movable member that is movable between two positions in whichthe bleed valve that is to be controlled is connected respectively tothe means for taking off air at the pressure P1, and to the ambientatmosphere, with the movement of the movable member being controlled bythe fluid under pressure delivered by the solenoid valve.
 5. A systemaccording to claim 1, wherein the solenoid valve has two inlets forconnecting respectively to a source of fluid under pressure and to theambient atmosphere, and an outlet connected to a port of the directionalcontrol valve.
 6. A system according to claim 1, wherein an inlet of thesolenoid valve is for connecting to means for taking off air at apressure P2 from the turbine engine, the pressure P2 being less than thepressure P1.
 7. A system according to claim 1, wherein the solenoidvalve has two chambers, one of which is for feeding a port of thedirectional control valve with fluid under pressure, and the other ofwhich is for connecting said port to the ambient atmosphere.
 8. Aturbine engine, comprising an engine surrounded by a nacelle andincluding at least one pneumatic valve, wherein said at least onepneumatic valve is controlled by a system according to claim
 1. 9. Aturbine engine according to claim 8, wherein the directional controlvalve is situated in the engine close to the bleed valve or in thenacelle close to the solenoid valve.